Time profiles of energy balance in dairy cows in association with metabolic status, inflammatory status, and disease

The early lactation period in dairy cows is characterized by complex interactions among energy balance (EB), disease, and alterations in metabolic and inflammatory status. The objective of this study was to cluster cows based on EB time profiles in early lactation and investigate the association between EB clusters and inflammatory status, metabolic status, oxidative stress, and disease. Holstein-Friesian dairy cows (n = 153) were selected and monitored for disease treatments during wk 1 to 6 in lactation. Weekly EB was calculated based on energy intake and energy requirements for maintenance and milk yield in wk 1 to 6 in lactation. Weekly plasma samples were analyzed for metabolic variables in wk 1 to 6, and inflammatory and oxidative stress variables in wk 1, 2, and 4 in lactation. Liver activity index (LAI) was computed from plasma albumin, cholesterol, and retino-binding protein concentration. First, cows were clustered based on time profiles of EB, resulting in 4 clusters (SP: stable positive; MN: mild negative; IN: intermediate negative; SN: severe negative). Cows in the SN cluster had higher plasma nonesterified fatty acids and β-hydroxybutyrate concentrations, compared with cows in the SP cluster, with the MN and IN cluster being intermediate. Cows in the SN cluster had a higher milk yield, lower dry matter intake in wk 1, lower insulin concentration compared with cows in the SP cluster, and lower glucose and IGF-1 concentration compared with cows in the SP and MN clusters. Energy balance clusters were not related with plasma haptoglobin, cholesterol, albumin, paraoxonase, and liver activity index (LAI). Second, cows were grouped based on health status [IHP: cows with treatment for inflammatory health problem (endometritis, fever, clinical mastitis, vaginal discharge or retained placenta); OHP: cows with no IHP but treatment for other health problem (milk fever, cystic ovaries, claw, and leg problems, rumen and intestine problems or other diseases); NHP: cows with no treatments, in the first 6 weeks after calving]. Energy balance was not different among health status groups. The IHP cows had lower nonesterified fatty acids and greater insulin concentration in plasma compared with OHP. The IHP cows had lower plasma albumin concentration, lower LAI and higher haptoglobin concentration compared with OHP and NHP. Overall, EB time profiles were associated with the metabolic status of dairy cows in early lactation, but were only limitedly related with markers of inflammation and oxidative stress status. Inflammatory and metabolic status were related to disease events in early lactation and caused prolonged effects on liver metabolism.

Analytical Validation of Two Assays for Equine Ceruloplasmin Ferroxidase Activity Assessment

Ceruloplasmin (Cp) assessment in biological samples exploits the oxidase activity of this enzyme against several substrates, such as p-phenylenediamine (p-P), o-dianisidine (o-D) and, most recently, ammonium iron(II) sulfate (AIS). Once developed in humans, these assays are often used in veterinary medicine without appropriately optimizing in the animal species of interest. In this study, two assays using AIS and o-D as substrates have been compared and validated for Cp oxidase activity assessment in horse's plasma. The optimization of the assays was performed mainly by varying the buffer pH as well as the buffer and the substrate molar concentration. Under the best analytical conditions obtained, the horse blood serum samples were treated with sodium azide, a potent Cp inhibitor. In the o-D assay, 500 µM sodium azide treatment completely inhibits the enzymatic activity of Cp, whereas, using the AIS assay, a residual analytical signal was still present even at the highest (2000 µM) sodium azide concentration. Even though the analytical values obtained from these methods are well correlated, the enzymatic activity values significantly differ when expressed in Units L-1. A disagreement between these assays has also been detected with the Bland-Altman plot, showing a progressive discrepancy between methods with increasing analytical values.

Relation between redox potential and natural antibody levels in goat kid serum

The redox potential and the natural antibody (NAb) levels are parameters commonly tested to verify the physiological response to stressful situations determined by farming conditions or research needs. In this paper, the redox potential, assessed by different spectrophotometric methods, was related to NAb levels together with total immunoglobulin (tot-Ig) levels in goat kid serum. Reactive oxygen metabolites (ROMs) and ceruloplasmin (CP) oxidase activity were significantly associated with NAb-IgG and NAb-IgM. Nitric oxide metabolites (NOx) and total thiol levels (TTLs) were significantly related to NAb-IgM and tot-IgM, and with NAb-IgG, respectively. A tendency was shown between ROMs and tot-IgM, and between CP and tot-IgM, where, however, the significance levels were above the cut-off values. Total oxidant status (TOS), total antioxidant activity (TAA), determined by the ABTS-based method, the ferric reducing ability of plasma (FRAP), and free radical scavenging activity (FRSA) were associated with neither NAb nor tot-Ig. The obtained results are discussed in light of the possible linkage between the (anti)oxidant status and the innate immune system in goats.

The relationship between dry period length and milk production of Holstein dairy cows in tropical climate: a machine learning approach

The objective of this retrospective longitudinal study was to evaluate the relationship between dry period length and the production of milk, fat, protein, lactose and total milk solids in the subsequent lactation of Holstein dairy cows under tropical climate. After handling and cleaning of the data provided by the Holstein Cattle Breeders Association of Minas Gerais, data from 32 867 complete lactations of 19 535 Holstein animals that calved between 1993 and 2017 in 122 dairy herds located in Minas Gerais state (Brazil) were analysed. In addition to dry period length, calving age, lactation length, milking frequency, parity, calf status at birth, herd, year, and season of calving were included in the analysis as covariables to account for additional sources of variation. The machine learning algorithms gradient boosting machine, extreme gradient boosting machine, random forest and artificial neural network were used to train models using cross validation. The best model was selected based on four error metrics and used to evaluate the variable importance, the interaction strength between dry period length and the other variables, and to generate partial dependency plots. Random forest was the best model for all production outcomes evaluated. Dry period length was the third most important variable in predicting milk production and its components. No strong interactions were observed between the dry period and the other evaluated variables. The highest milk and lactose productions were observed with a 50-d long dry period, while fat, protein, and total milk solids were the highest with dry period lengths of 38, 38, and 44 d, respectively. Overall, dry period length is associated with the production of milk and its components in the subsequent lactation of Holstein cows under tropical climatic conditions, but the optimum length depends on the production outcome.

Effect of dry period length on plasma minerals and oxidative stress around parturition and milk yield in high-producing Holstein dairy cows

The aim of present study was to evaluate the effect of dry period length (56 vs. 28 days) on plasma minerals, albumin, total protein and globulin, oxidative status, and milk production in high-producing dairy cows (13,500 ± 1800 kg milk in previous 305-day lactation). A total of 120 multiparous Holstein cows were used in a repeated measurement mixed model (animal was considered random effect) with two experimental groups and 60 replicates each: 1-long dry period (LDP, 56-day dry period) and 2-short dry period (SDP, 28-day dry period). While LDP cows received two different rations in far-off and close-up periods (DCAD = 189 and - 130 Meq/Kg, respectively), the SDP cows received only the close-up ration (- 130 Meq/Kg) without passing the far-off stage. Blood samples for minerals, oxidative stress, and metabolites (albumin, total protein) were collected on calving day, 24 and 48 h after parturition. Milk samples of all cows in each group were collected monthly (four months from parturition to 120 DIM) and analyzed for milk fat, protein, and somatic cell count (SCC). Results showed that SDP had no effect on plasma calcium (Ca), ionized calcium (iCa), magnesium (Mg), and phosphorus (iP). Total antioxidant capacity (TAC) in the SDP cows was higher (P < 0.05) than the LDP cows. The treatment had no significant effect on plasma concentration of total protein, albumin, globulin, and superoxide dismutase (SOD) activity. A positive significant (P < 0.05) correlation was observed between plasma Mg and TAC in SDP group. Short dry period reduced (P < 0.05) milk production (48.39 vs. 51.95 kg/day; about 7%) during the first 120 days in milk. However, SDP cows had higher (P < 0.05) milk protein content compared to LDP group. The log-transformed of somatic cell count (LnSCC) was not affected by the treatment. It was concluded that a short dry period (28 days) had no negative effect on plasma Ca, iCa, Mg, and iP and even could improve TAC in high-producing Holstein cows.

Calf and dam characteristics and calf transport age affect immunoglobulin titers and hematological parameters of veal calves

This study aimed to investigate effects of transport age of calves (14 vs. 28 d), and of calf and dam characteristics, on immunoglobulin titers and hematological variables of veal calves. Calves (n = 683) were transported to a veal farm at 14 or 28 d of age. Natural antibodies N-IgG, N-IgM, and N-IgA against phosphorylcholine conjugated to bovine serum albumin (PC-BSA) were measured in serum of the dams 1 wk before calving and in first colostrum. These antibodies were also measured in serum of calves 1 wk after birth, 1 d before transport, and in wk 2 and 10 posttransport at the veal farm. Hematological variables were assessed in calves 1 d before transport and in wk 2 posttransport. One day before transport, titers of N-IgG, N-IgM, N-IgA, and neutrophil counts were higher, and lymphocyte counts were lower in 14-d-old calves compared with 28-d-old calves. In wk 2 at the veal farm, calves transported at 14 d of age had higher N-IgG titers and neutrophil counts, but lower N-IgM and N-IgA titers, and lymphocyte counts than calves transported at 28 d. In wk 1 and 1 d before transport, N-Ig in calves were positively related to N-Ig in colostrum. In wk 2 and 10 at the veal farm, N-IgG in calves was positively related to N-IgG in colostrum. The N-IgG titers in calves at the dairy farm were negatively related to the likelihood of being individually treated with antibiotics or other medicines at the veal farm. Our results suggest that calves transported to the veal farm at 28 d of age showed a more advanced development of their adaptive immunity than calves transported at 14 d of age. Quality of colostrum might have long-term consequences for N-IgG titers and immunity in veal calves.

Effects of Pasture Type on Metabolism, Liver and Kidney Function, Antioxidant Status, and Plant Secondary Compounds in Plasma of Grazing, Jersey Dairy Cattle During Mid-lactation

Some pasture species are rich in phytochemicals, able to improve milk yield and quality and to reduce the environmental impacts of livestock farming. The phytochemicals interact with the different gene networks within the animal, such as nuclear factor erythroid 2-related factor 2 (NRF2), but their overall impact on animal health remains to be fully understood. The objective of this study was to identify the effects of pasture Legumes and non-leguminous Forbs containing high bioactive compounds on metabolism and activity of the liver, antioxidant response, kidney function, and inflammation of dairy cows using a large array of blood parameters associated with metabolism and the innate immune system. For this purpose, 26 parameters and the concentration of certain bioactive compounds were assessed in blood plasma, collected from the Jersey cows grazing either Grass, Legume, or Forb-based pastures. In addition, serum collected from all the cows was utilized to detect the changes in NRF2 activation in bovine mammary alveolar cells (MACT) and hepatocytes. Compared with Grass, the cows that grazed both Forb and Legume pastures had lower β-hydroxybutyric acid (BHB) and creatinine and larger vitamin E and the ferric reducing ability of the plasma, supporting an improved antioxidative status for these animals. Compared with both Grass and Legume, the cows that graze Forb pasture had lower urea and urea to creatinine ratio, and lower creatinine, indicating a better kidney function. The cows grazing Legume pasture had greater hematocrit, bilirubin, cholesterol, albumin, β-carotene, retinol, and thiol groups but lower ceruloplasmin, paraoxonase, and myeloperoxidase (MPO) than those grazed Grass and Forb pastures, indicating a positive effect of Legume pasture on the liver, oxidative stress, and red blood cells. The plasma of cows in the various pastures was enriched with various isoflavonoids, especially the cows grazed on Forb and Legume pastures, which likely contributed to improving the antioxidative status of those cows. However, this effect was likely not due to the higher activation of NRF2. Overall, these results indicate that Forb and Legume pastures rich in secondary metabolites do not strongly affect the metabolism but can improve the status of the liver and the kidney and improve the efficiency of N utilization and antioxidant response, compared with the Grass pasture.

Adipokines as biomarkers of postpartum subclinical endometritis in dairy cows

Adipokines emerged as regulators of metabolism and inflammation in several scenarios. This study evaluated the relationship between adipokines (adiponectin, chemerin and visfatin) and cytological (subclinical) endometritis, by comparing healthy (without), transient (recovered by 45 days postpartum (DPP)) and persistent (until 45 DPP) endometritis cows (n = 49). Cows with persistent endometritis had higher adiponectin concentrations in plasma (at 21 DPP, P < 0.05 and at 45 DPP, P < 0.01) and in uterine fluid (at 45 DPP, P < 0.001), and higher chemerin concentrations in plasma (P < 0.05) and uterine fluid (P < 0.01) at 45 DPP than healthy cows. Cows with persistent endometritis had higher gene transcription in the cellular pellet of uterine fluid and protein expression in the endometrium of these adipokines and their receptors than healthy cows. Adiponectin plasma concentrations allowed to discriminate healthy from persistent endometritis cows, in 87% (21 DPP) and 98% (45 DPP) of cases, and adiponectin and chemerin uterine fluid concentrations at 45 DPP allowed for this discrimination in 100% of cases. Cows with concentrations above the cutoff were a minimum of 3.5 (plasma 21 DPP), 20.4 (plasma 45 DPP), and 33.3 (uterine fluid 45 DPP) times more at risk of evidencing persistent endometritis at 45 DPP than cows with concentrations below the cutoff. Overall, results indicate a relationship between adipokine signalling and the inflammatory status of the postpartum uterus of dairy cows, evidencing that adipokines represent suitable biomarkers of subclinical endometritis, able to predict the risk of persistence of inflammation.

Relationships between metabolic profiles and gene expression in liver and leukocytes of dairy cows in early lactation

Homeorhetic mechanisms assist dairy cows in the transition from pregnancy to lactation. Less successful cows develop severe negative energy balance (NEB), placing them at risk of metabolic and infectious diseases and reduced fertility. We have previously placed multiparous Holstein Friesian cows from 4 herds into metabolic clusters, using as biomarkers measurements of plasma nonesterified fatty acids, β-hydroxybutyrate, glucose and IGF-1 collected at 14 and 35 d in milk (DIM). This study characterized the global transcriptomic profiles of liver and circulating leukocytes from the same animals to determine underlying mechanisms associated with their metabolic and immune function. Liver biopsy and whole-blood samples were collected around 14 DIM for RNA sequencing. All cows with available RNA sequencing data were placed into balanced (BAL, n = 44), intermediate (n = 44), or imbalanced (IMBAL, n = 19) metabolic cluster groups. Differential gene expression was compared between the 3 groups using ANOVA, but only the comparison between BAL and IMBAL cows is reported. Pathway analysis was undertaken using DAVID Bioinformatic Resources (https://david.ncifcrf.gov/). Milk yields did not differ between BAL and IMBAL cows but dry matter intake was less in IMBAL cows and they were in greater energy deficit at 14 DIM (-4.48 v -11.70 MJ/d for BAL and IMBAL cows). Significantly differentially expressed pathways in hepatic tissue included AMPK signaling, glucagon signaling, adipocytokine signaling, and insulin resistance. Genes involved in lipid metabolism and cholesterol transport were more highly expressed in IMBAL cows but IGF1 and IGFALS were downregulated. Leukocytes from BAL cows had greater expression of histones and genes involved in nucleosomes and cell division. Leukocyte expression of heat shock proteins increased in IMBAL cows, suggesting an unfolded protein response, and several key genes involved in immune responses to pathogens were upregulated (e.g., DEFB13, HP, OAS1Z, PTX3, and TLR4). Differentially expressed genes upregulated in IMBAL cows in both tissues included CD36, CPT1, KFL11, and PDK4, all central regulators of energy metabolism. The IMBAL cows therefore had greater difficulty maintaining glucose homeostasis and had dysregulated hepatic lipid metabolism. Their energy deficit was associated with a reduced capacity for cell division and greater evidence of stress responses in the leukocyte population, likely contributing to an increased risk of infectious disease.

Incidence and risk factors for reproductive disorders in organic certified dairies

The objective was to determine the lactational incidence risks of reproductive disorders (RD) including dystocia (DYS), retained fetal membranes (RFM), puerperal metritis (PM), clinical endometritis (CE), pyometra (PYO), late pregnancy loss (LPL), and culling due to reproductive reasons (CRR) in large organic certified dairies with predominant use of Holstein genetics. In addition, potential risk factors for RD, including parity category, milk yield in the previous lactation, season of dry-off, access to grazing at dry-off, length of the dry period (DPL), length of the close-up period (CUPL), calculated gestation length (CGL), season of calving, access to grazing at calving, concurrent health conditions, and total number of artificial inseminations were analyzed. A retrospective study was performed using information from 8 organic certified herds located in northern Colorado and west Texas, ranging from 900 to 6,000 milking cows. Cow information consisted of finalized lactations starting with calvings occurring between January 1, 2016, and December 31, 2018. Data were analyzed using time-to-event analyses and multivariable logistic regression. Clinical endometritis had the greatest lactational incidence risk (incidence risk = 10.1%; 95% CI = 9.8-10.3%), followed by DYS (8.8%; 8.5-9.1%), PM (4.9%; 4.7-5.1%), PYO (4.0%; 3.8-4.1%), LPL (3.6%; 3.4-3.7%), and RFM (2.0%; 1.8-2.1%). The incidence risk of CRR was 7.5% (7.3-8.7%), representing 29.1% (28.4-30.0%) of all culling reasons. Median time from calving to diagnosis of PM, CE, PYO, and LPL were 6, 23, 111, and 228 d, respectively. Median time for CRR was 391 d. The main risk factors for RD were DPL, CGL, and CUPL. Season of dry-off was a risk factor for RFM, PM, CE, LPL, and PYO. Short DPL (<30 d) was associated with increased odds (95% CI) of RFM [2.1 (1.6-2.7)], PM [1.4 (1.2-1.7)], and LPL [2.5 (1.5-4.2)]. Shortened CGL (<270 d) increased the odds of DYS [1.5 (1.3-1.8)], RFM [3.2 (2.4-4.1)], and PM [2.4 (1.7-3.3)], whereas extended CGL (>285 d) increased the odds of DYS [1.5 (1.4-1.7)], PM [1.5 (1.2-2.0)], CE [1.5 (1.1-2.0)], and CRR [1.2 (1.10-1.4)]. Shortened CUPL was associated with increased odds of all the RD. Cows spending less than 7 d in the close-up groups had greater odds of DYS [1.4 (1.1-1.8)], RFM [2.1 (1.8-2.4)], PM [1.9 (1.6-2.1)], PYO [1.5 (1.2-1.8)], LPL [2 (1.7-2.3)], and CRR [1.4 (1.04-1.8)] compared with cows spending more than 14 d in the close-up group. Season of calving was associated with the odds of PM [summer = 1.13 (1.01-1.2)], PYO [summer = 1.7 (1.1-2.5)], and LPL ([fall = 0.8 (0.6-0.96)] compared with winter calving. Other risk factors affecting RD were parity number, total number of artificial inseminations, and concurrent health conditions. Overall, lactational incidence risks of reproductive diseases were comparable with those reported in conventional herds. The identified risk factors for RD open opportunities for interventions, especially focused in precalving management, estimation of due dates, and closer monitoring of pregnancies from natural services in large organic certified dairy herds.

Paraoxonase 1 in bovine milk and blood as marker of subclinical mastitis caused by Staphylococcus aureus

The aim of this study was to determine serum lipid values and parameters of oxidative stress in blood and milk of cows with subclinical mastitis (SCM) caused by Staphylococcus aureus and to establish association between these parameters. The study was performed on total of 104 cows assigned into control group of healthy animals (n = 12) and two groups of cows with SCM, either SCM₁ group (n = 37) with ˂ 1000 CFU/mL of S. aureus or SCM₂ group (n = 55) with ≥1000 CFU/mL of causative agent in milk. Significantly lower serum concentrations of high density lipoprotein-cholesterol (HDLC) in SCM₂ group and higher low density lipoprotein-cholesterol (LDL-C) in both SCM groups were recorded. Significantly lower paraoxonase-1 (PON1) activity and higher lipid hydroperoxides (LOOH) concentration in blood and milk were recorded in both groups of SCM cows vs control. In blood serum of cows from SCM₂ group significantly higher concentrations of hydrogen peroxide (H₂O₂) and malondialdehyde (MDA), but significantly lower total antioxidative capacity (TAC) were obtained. In milk serum of SCM cows were detected significantly higher concentrations of H₂O₂ and MDA, but significantly lower TAC vs control. There was a significant positive correlation between PON1 in serum with HDLC, but negative correlation with LDL-C and LOOH. In milk, PON1 negatively correlated with LOOH and somatic cell counts (SCC). Strong positive correlation was obtained between PON1 in blood and milk. Oxidative stress and inflammatory reaction induced by SCM significantly lowered PON1 activity in blood and milk of affected cows.

Relationship between inflammatory biomarkers and oxidative stress with uterine health in dairy cows with different dry period lengths

Earlier studies indicated that the inflammatory status of dairy cows in early lactation could not be fully explained by the negative energy balance (NEB) at that moment. The objective of the present study was to determine relationships between inflammatory biomarkers and oxidative stress with uterine health in dairy cows after different dry period lengths. Holstein-Friesian dairy cows were assigned to one of three dry period lengths (0-, 30-, or 60-d) and one of two early lactation rations (glucogenic or lipogenic ration). Cows were fed either a glucogenic or lipogenic ration from 10-d before the expected calving date. Part of the cows which were planned for a 0-d dry period dried themselves off and were attributed to a new group (0 → 30-d dry period), which resulted in total in four dry period groups. Blood was collected (N = 110 cows) in weeks -3, -2, -1, 1, 2, and 4 relative to calving to determine biomarkers for inflammation, liver function, and oxidative stress. Uterine health status (UHS) was monitored by scoring vaginal discharge (VD) based on a 4-point scoring system (0, 1, 2, or 3) in weeks 2 and 3 after calving. Cows were classified as having a healthy uterine environment (HU, VD score = 0 or 1 in both weeks 2 and 3), nonrecovering uterine environment (NRU, VD score = 2 or 3 in week 3), or a recovering uterine environment (RU, VD score = 2 or 3 in week 2 and VD score= 0 or 1 in week 3). Independent of dry period length, cows with NRU had higher plasma haptoglobin (P = 0.05) and lower paraoxonase levels (P < 0.01) in the first 4 weeks after calving and lower liver functionality index (P < 0.01) compared with cows with HU. Cows with NRU had lower plasma albumin (P = 0.02) and creatinine (P = 0.02) compared with cows with a RU, but not compared with cows with HU. Independent of UHS, cows with a 0 → 30-d dry period had higher bilirubin levels compared with cows with 0-, 30-, or 60-d dry period (P < 0.01). Cows with RU and fed a lipogenic ration had higher levels of albumin in plasma compared with cows with NRU and fed a lipogenic ration (P < 0.01). In conclusion, uterine health was related to biomarkers for inflammation (haptoglobin and albumin) and paraoxonase in dairy cows in early lactation. Cows which were planned for a 0-d dry period, but dried themselves off (0 → 30-d dry period group) had higher bilirubin levels, which was possibly related to a more severe NEB in these cows. Inflammatory biomarkers in dairy cows in early lactation were related to uterine health in this period.

Redox Biology in Transition Periods of Dairy Cattle: Role in the Health of Periparturient and Neonatal Animals

Dairy cows undergo various transition periods throughout their productive life, which are associated with periods of increased metabolic and infectious disease susceptibility. Redox balance plays a key role in ensuring a satisfactory transition. Nevertheless, oxidative stress (OS), a consequence of redox imbalance, has been associated with an increased risk of disease in these animals. In the productive cycle of dairy cows, the periparturient and neonatal periods are times of increased OS and disease susceptibility. This article reviews the relationship of redox status and OS with diseases of cows and calves, and how supplementation with antioxidants can be used to prevent OS in these animals.

Relationship between the degree of antioxidant protection and the level of malondialdehyde in high-performance Polish Holstein-Friesian cows in peak of lactation

Lipid peroxidation can be described as a process under which free radicals attack carbon double bonds of omega-3 and omega-6 fatty acids. Whereas the end products of this process are reactive aldehydes, such as malondialdehyde (MDA). Lipid peroxidation leads to adverse changes in the nutritional value of milk; therefore, higher degree of antioxidant protection (DAP) ensures higher stability of dairy products by effecting their high antioxidative potential. Therefore, the purpose of this study was to demonstrate the relationship between the DAP and the level of MDA in high-performance Polish Holstein-Friesian cows in peak of lactation. Sixty-three Polish Holstein-Friesian cows were selected to the experiment according to: parity (all in the 2nd lactation), phase of lactation (peak of lactation), cytological quality of milk (somatic cell count < 150 thousand/ml) and without diagnosed metabolic diseases. The data obtained were analyzed statistically by two-way ANOVA, and Tukey's post-hoc test. After analysis of performance the cows were divided into 3 groups (twenty one cows in each group) based on milk yield and MDA concentration. The study revealed a significant effect of the lactation performance of cows on MDA levels in milk (P ≤ 0.01). The highest concentration of MDA (61.137 nM/mL) was shown in milk of cows yielding between 50.00 and 55.80 kg/day. The highest concentration of fat was found in milk in which the MDA level ranged from 48 to 86 nM/mL. Whereas, the inverse relationship was demonstrated in case of protein concentration. The highest level of protein was found in cows with MDA levels in the range of 18-28 nM/mL (P ≤ 0.01). The lowest MDA level (in the range of 18-28 nM/mL) was associated with the highest concentration of vitamin E, β-carotene, total antioxidant status (TAS) and DAP, measured in both milk and plasma. The obtained results show that lipid peroxidation leads to adverse changes in the nutritional value of milk; the highest DAP (7.89 x 10-3) was found in the cows with the lowest MDA concentration in milk.

Haptoglobin and serum amyloid A as putative biomarker candidates of naturally occurring bovine respiratory disease in dairy calves

Bovine respiratory disease (BRD) is one of the leading causes of morbidity and mortality in dairy calves. Identification of reliable biomarkers of naturally occurring BRD is essential for ensuring early diagnosis and treatment of calves and monitoring treatment efficacy. This need is punctuated, especially in mild to moderate cases that would greatly help to decrease recurrence and the overall prevalence of BRD. The present study was conducted to investigate the changes in serum concentrations of haptoglobin (Hpt) and serum amyloid A (SAA) and association between oxidative stress and acute phase proteins (APPs) in BRD. Hpt and SAA levels significantly increased (P < .01) in BRD stressed calves as compared to healthy subjects. There was a significant decrease (P < .01) in serum albumin (Alb) concentration of infected calves as compared to controls. The oxidative stress markers revealed a significant (P < .01) increase in lipid peroxidation (LPO) and a concurrent decrease in activities of superoxide dismutase (SOD), reduced glutathione (R-GSH) and catalase (CAT) in BRD. A significant correlation among APPs, extent of oxidative stress and clinical score (CS) of calves was depicted. A stepwise decrease in Hpt and SAA and increase in Alb was observed in infected calves post-treatment. These results suggest implication of oxidative stress in enhancing APPs and monitoring of APPs as a potential complement to clinical assessment of treatment in calves with naturally occurring BRD. Hpt may be useful as the most sensitive biomarker in BRD. However, the combined use of Hpt and oxidative stress biomarkers would greatly improve the diagnostic accuracy.